In the treatment and care of turf such as grass or other ground covers of lawns, golf courses, softball fields and the like, it is highly desirable to aerate the turf so as to enable air, moisture and nutrients to reach the roots of the grass, etc. The aeration of turf is generally performed by forming a pattern of holes in the turf. This tends to disturb the soil and roots beneath the surface of the ground cover, and when moisture and fertilizers are applied to the turf the root structure of the turf is able to directly absorb these nutrients and thereby the growth of the root structure is stimulated, making the turf healthier.
Some prior art aerators have a plurality of coring tines which penetrate the soil and cut a generally cylindrical core or plug in the turf, and when the coring tines are removed from the turf, they usually lift the core out of the ground, leaving a residue of cores of soil on the surface of the ground. The residue of cores of soil is undesirable on lawns and on playing fields such as golf courses and baseball fields where the condition of the surface of the turf is very important to the sports person. A type of core producing aerator is disclosed in U.S. Pat. No. 4,773,486.
U.S. Pat. No. 5,029,652 disclosed an improved turf aerator that includes rotary hoes mounted about a laterally extending drive shaft that “walk” or rotate like a wheel along the ground in response to forward movement of the aerator and which wobble when the drive shaft is rotated. This combination of movements causes the tines of the rotary hoes to form holes in the soil that are larger in lateral dimensions than the width of the tines, and the tines tend to penetrate the soil with less weight being required to force the tines into the soil than the previously known aerators. The tines usually do not leave a residue of dirt or roots on the surface of the turf, therefore providing a smooth surface suitable for sports activities.
In order to wobble the tines of the rotary hoes in response to the rotation of the drive shaft, the bearings that support the rotary hoes on the drive shaft are mounted with their axes of rotation angled with respect to the axis of rotation of the drive shaft. The axes of rotation of the bearings are angled with respect to the drive shaft by placement of a pair of duplicate bearing adapters on the drive shaft at the position of each rotary hoe, with each bearing supported by two of the bearing adapters. The bearing adapters are press fit into opposite ends of the central cylindrical opening of the bearing.
The above identified bearing adapters have an angled interior hexagonal shaft opening to be positioned on the hexagonal drive shaft. The angled shaft opening of the bearing adapters results in the outer race of each adapter to be larger on one side of the adapter. The bearing adapters are oriented 180 degrees from each other about the hexagonal drive shaft so that the larger outer races of the adapters were positioned on opposite sides of the hexagonal drive shaft. Since the bearing adapters are fitted from opposite sides in the opening of the bearing that supports the rotary hoes, the annular bearing surfaces of the bearings were sloped with respect to the longitudinal centerline of the drive shaft.
The rotary hoes rotated freely about the angled bearings and when the drive shaft was rotated, the bearings and the rotary hoes would wobble. And when the turf aerator was moved in a forward direction, the rotary hoes would “walk” through the turf and wobble at the same time. This walking and wobbling motion caused the tines of the rotary hoes to form openings in the turf that were larger in the bottom of the openings than at the surface of the turf, which was a very desirable improvement over the prior art. This is disclosed in more detail in U.S. Pat. No. 5,209,306, the disclosure of which is adopted herein by reference in its entirety.
While the operation of the above described prior art aerator has proven to be satisfactory, problems have been encountered when manufacturing, repairing and/or replacing the bearings and bearing adapters of the type as described in U.S. Pat. No. 5,209,306. The drive shaft on which the bearing adapters are mounted have six external flats, and both bearing adapters for each bearing have a corresponding number of internal flats that must register with the external flats of the drive shaft in order to rotate in unison with the drive shaft. In order to properly tilt the bearing with the bearing adapters, the bearing adapters must be 180 degrees out of phase with each other. There are times when a worker that press fits the bearing adapters into opposite ends of the cylindrical bearing does not position the bearing adapters 180 degrees out of phase with each other. When this happens, the bearing mount surfaces of the bearing adapters will not be concentric, thereby improperly supporting the facing surfaces of the bearing. The misalignment of the bearing adapters, 180° timing, causes both preloaded static stress and operational stress which is likely to result in premature bearing failure.
If the operator of the cultivator recognizes that there is a faulty bearing assembly on his/her cultivator, the usual procedure is for the worker to disassemble the drive shaft and its adapters and bearings, replace the bad bearing, and reassemble bearing assemblies and the rotary hoes on the drive shaft.
Also, the prior art bearing adapters are press fit into opposite ends of the cylindrical opening of their bearings and the inner ends of the bearing adapters do not completely meet each other inside the cylindrical opening of the bearings. This forms a circular space between the adapters inside of the bearing, creating a void in which debris, moisture and scale is likely to accumulate. If the interior bearing fails, then all bearings that are taken off the drive shaft are replaced. When the bearing assemblies are disassembled from the drive shaft, the cones of the bearings tend to separate and dirt and trash fall between the bearing cones and contaminate the bearing. Because of this design, it is likely that the rotary hoes will become contaminated when being removed from the drive shaft.
Another potential problem is the accuracy in which the adapters are shaped. For example, when machining the adapters it is possible to form the sloped surfaces of the adapters that impart the angle of the bearing and rotary hoe at a slightly incorrect angle. If one bearing adapter is inaccurately formed and its mate accurately formed, the bearing assembly becomes preloaded with stress. Further, when a pair of bearing adapters with the same error are used to support one bearing, and since the adapters are mounted 180 degrees out of phase with each other, the design error is likely to double the alignment error of the bearing adapters on the drive shaft.
Accordingly, it can be seen that it would be desirable to produce a turf aerator that may be accurately designed and assembled, longer lasting, and which performs the function of aerating turf while significantly reducing compaction of the soil and without leaving cores of soil on the ground surface, and which forms openings in the surface of the turf and disturbs the soil to stimulate the growth of the root structure of the ground cover.
It would be desirable to produce a bearing assembly for use in a turf aerator that creates a side-to-side wobbling of rotary hoes, with the bearing assembly being shaped to avoid misassembly of its parts, disassembly without contamination, and eliminate manufacturing errors by having a single journal adapter.